JPS5818132B2 - Carbon monoxide containing air treatment equipment - Google Patents

Description

Detailed Description of the Invention The present invention relates to a processing device for converting air containing carbon monoxide into less harmful carbon dioxide using a catalyst. It is applied to air streams from which carbon monoxide should be removed.

The toxicity of carbon monoxide is well known, and even though most people are aware that it is an extremely dangerous and harmful gas, there are still cases of poisoning and death.

Even in environmental administration, efforts are being put into various exhaust gas regulations and thorough precautions when using indoor combustion appliances in order to prevent air pollution and indoor poisoning accidents. The current situation is as described above.

The present invention relates to a purification device using a new type of catalyst for removing carbon monoxide.

Carbon monoxide purification technology has made remarkable progress in recent years, primarily in automobile exhaust gas purification technology, which was first required in the form of legal regulations.

There are a large number of catalysts that are used to purify carbon monoxide and hydrocarbons in automobile exhaust gas1, but their performance has been studied in response to the requirements for automobiles, and the activity of all of them has been Most require a temperature of 100°C or higher.

A typical catalyst thereof is, for example, a catalyst in which a platinum metal element is supported on an activated alumina carrier.

Conventionally, catalysts that are effective at temperatures below 100°C lose their effectiveness at temperatures below 40°C, deteriorate in the coexistence of water vapor, and have no stable performance.

Carbon monoxide is generated through the combustion of petroleum fuel, but the combustion itself is used as a primary energy source, whether used for consumer or industrial purposes, either as heat or converted into another form of energy. There is 1.

The exhaust gas temperature is related to the efficiency of such a heat engine or heat utilization equipment.

Internal combustion engines have low thermal efficiency and have extremely high exhaust temperatures, but household appliances and other devices with high thermal efficiency have relatively low exhaust temperatures.

From the perspective of effective energy use, the trend towards energy saving will continue to increase, and technological developments such as improvements in thermal efficiency and waste heat recovery will be promoted, but in this case the exhaust gas temperature will tend to decrease.

In response to these conditions, the present invention is intended to be applied to household combustors with high thermal efficiency, and in extreme cases, to purify carbon monoxide contained in air flows with almost no heat flow. It was measured.

There is no conventional purification device that is sufficiently effective at temperatures as low as 100°C or lower.

The carbon monoxide-containing air treatment device of the present invention will be explained below.

The present inventors have already discovered that a catalyst consisting of a cured product containing powdered activated carbon, an alkali, and a cement agent as main components and supporting one or more platinum metal elements has excellent carbon monoxide purification ability at around room temperature. I discovered that.

The present invention has been developed as an apparatus for actually performing gas purification treatment by applying this catalyst.

The most important feature of the catalyst, which uses a cured composition containing powdered activated carbon, an alkali, and a cementing agent, and supports one or more platinum metal elements on this is the composition carrier.
The alkali used therein is preferably an alkali metal hydroxide or carbonate having a high solubility since the production method involves adding water and kneading and molding.

Also, as a cement agent, any material that forms a stable porous body as a hydraulic material will be effective to some extent.
In particular, in the case of alkaline earth metal aluminates, a significantly highly active support can be obtained due to the promoter effect.

Among them, alumina cement whose main component is lime aluminate is the best.

As a specific example of the above-mentioned catalyst, the performance of one using a carrier mainly composed of potassium carbonate, lime aluminate, and powdered activated carbon is shown in FIG.

There is an optimal range for the combination of potassium carbonate, lime aluminate, and powdered activated carbon, including potassium carbonate (5-15%), powder.

Activated carbon (10-50%)1. The balance should be lime aluminate (all percentages by weight).

The catalyst exhibiting the characteristics shown in Figure 1 was prepared by using a mixed composition consisting of 1 part of potassium carbonate, 3 parts of powdered activated carbon, and 6 parts of lime aluminate (weight ratio), and to which platinum and palladium were each added. - 0.3% of the weight of each carrier was supported.

The catalyst activity evaluation conditions were a constant saturated absolute water content at 15°C, a space velocity of 5V = 50,000 (h-1), and an inlet CO concentration i.
o o pprn.

Figure 1 shows the temperature and C when the catalyst packed bed temperature is changed.
o The relationship with conversion rate is shown.

Although the catalyst of the present invention was tested with a particle size of 6 to 10 meshes, the reaction of the catalyst was completely controlled by external mass transfer.
The following reaction occurred, indicating that the activity of the catalyst itself was extremely excellent.

Next, the catalyst adjustment method will be explained.

First, the carrier composition is prepared by kneading each raw material with water and granulating it, for example, by extrusion molding.

This is made into a predetermined particle size and impregnated in an aqueous solution of chloroplatinic acid and palladium chloride, adsorbed on the surface, reduced with a reducing agent such as sulfur boron hydride, and then dried. .

Each raw material is powdered activated carbon, potassium carbonate, and lime aluminate, and the amount of precious metal supported is 0.3wt each in a reduced state.
%, and the reduction method is boron hydride.
The reaction was carried out by adding 10 times the reduction equivalent in molar amount.

The reason for the high activity as described above will be explained below.

Potassium carbonate realizes the reduction of noble metals from the hydroxide state by dissolving a part of it into the aqueous solution, which not only helps in high activation and increases the specific surface area.
This contributes to the activation of activated carbon, which is presumed to have some kind of promoter effect.

On the other hand, as a cement agent, it plays a role as a stable binder for each component, and is also related to the pore physical properties of a porous hardened material. An effect can be obtained in which the catalytic effect contributes to the reactivity of the catalyst in the coexistence of water vapor.

FIG. 2 shows the relationship characteristics of the same catalyst with the relative humidity Co conversion rate.

The inlet concentration is constant at approximately 1 ooppm, the space velocity is constant at 30,000 (h-'), and the packed bed temperature is constant at 30°C.

The relative humidity is changed by changing the bypass ring flow rate.

In the case of FIG. 2, the particle size of the catalyst is as fine as 8 to 20 meshes, unlike the case of the temperature characteristics described above.

Therefore, a relatively high removal rate was obtained overall.

From FIG. 2, compared to the case of dry air, the Co conversion rate increases as the relative humidity increases.

This tendency shows a peak at about 50%, and as the humidity further increases, the Co conversion rate decreases.

A high removal rate can be obtained in a humidity range of about 20% to 80%.

When the target is the general atmosphere or combustion exhaust gas, the relative humidity is mostly within this range, so from that point of view, the properties of this catalyst are practical.

The reason why the catalyst exhibits high catalytic activity in the presence of water vapor is that, in terms of reaction rate, in the case of completely dry air, the rate-limiting surface reaction is of the inverse linear type with respect to the CO concentration, whereas the Another analysis has revealed that in the case of contained air, the CO concentration is controlled by a fractional CO2 desorption rate.

It is presumed that this catalyst is involved in the elementary reaction stage of water vapor in the reaction between CO and 0□, increasing the reaction rate.

Figure 3 shows the relationship between CO concentration and CO conversion rate for the same catalyst.

The particle size is the same as in FIG.

In FIG. 3, the space velocity is constant at 30,000 (h-'), the temperature is adjusted to 30° C., and the relative humidity is adjusted to 50%.

In Figure 3, the lowest concentration of 25pplIl
The removal rate trend decreases at the concentration of , but the reason for this is unclear.

Under such conditions, an adsorption-type rate formula (that is, a fractional CO2 desorption rate-limiting type) is used, so that the removal rate is higher on the lower concentration side.

FIG. 4 shows a carbon monoxide-containing air treatment device in one embodiment of the present invention.

In FIG. 4, 1 is the main body of the device, which has a fan 3 and a motor 2.

To illustrate the operation of the main body 1 of the device, the rotation of the motor 2 causes the fan 2 to
starts and air flows a, b, c, d, e, f are generated.

4 is a flange for connecting to another device or an exhaust gas flow path, and is fixed with screws or the like.

5 is a secondary air inlet provided to dilute the air flow 9.

This is the name of mixing as C style.

In order to complete the air flow between the two, various conventionally known mixing methods can be applied.

6 is a catalyst packed bed forming the main part of the carbon monoxide-containing air treatment device of the present invention.

The carbon monoxide contained in the air stream 9 is removed (converted) through the above process.

In Figure 4, the inflow of secondary air is due to the characteristics of the catalyst.
The removal rate is higher on the lower concentration side (see Figure 3),
In addition, at temperatures above 30°C, the region is completely dominated by diffusion, so even if the temperature drops, as long as the temperature is guaranteed to be above 30°C, there will be almost no change in performance, which is advantageous in terms of reaction. Become.

When the catalyst is placed in a high temperature state, it has some difficulty in high temperature stability because it contains activated carbon as a component.

In terms of temperature stability, it is estimated that it is completely stable for about 10,000 hours at a temperature of 100°C.

As for the effect of temporary temperature rise, it is stable even when heated to about 400°C.

From the background described above, the configuration of a catalyst device that uses secondary air to dilute it is extremely rational.

Next, as a specific structure of the catalyst packed bed to be applied to the apparatus shown in FIG. 4, the structures shown in FIGS. 5, 6, and 8 are possible.

Figure 5 shows a mesh frame shaped like a lunch box filled with granulated products.

Figure 6 shows a sheet (Figure 7) in which a granulated product is wrapped in a sandwich shape using two pieces of non-woven fabric, which is rolled into a cylindrical shape and the other end is closed. , which disperses the flow in the radial direction.

FIG. 8 shows a honeycomb-shaped catalyst which is a plate-shaped molded product and has a plurality of holes penetrating from one side to the opposite side.

Due to the characteristics of this catalyst, in the temperature range in which it is used, it is mostly external diffusion-dominated, so the catalyst configuration shown in FIG. 8 is advantageous in terms of purification performance and pressure loss.

Judging from the humidity characteristics shown in Figure 2, if the relative humidity is below 20% or above 80%, it would be better to install a humidifier/dehumidifier upstream and use it in conjunction with it. You can get a delicious confection.

Normally, humidification and dehumidification aim at a level of relative humidity of about 50%', so in view of the performance of the catalyst, it is desirable to install a humidification and dehumidification device to obtain the best effect.

In FIG. 4, a blower is used for forced ventilation, but if a sufficient upward flow can be obtained by natural convection, a blower is not necessary.

As described above, the carbon monoxide-containing air treatment device of the present invention is an extremely simple device that is added to household combustion appliances, air conditioners, air conditioners, etc., and removes and purifies carbon monoxide, which was previously considered to be extremely difficult. Carbon monoxide is almost completely purified even in an atmosphere at a low temperature, for example, 100° C. or less, and it has an excellent effect of improving the pollution situation.

[Brief explanation of drawings]

Figure 1 is a characteristic diagram showing the relationship between the packed bed temperature and CO conversion rate of the catalyst, Figure 2 is a characteristic diagram showing the relationship between relative humidity and CO conversion rate for the same catalyst, and Figure 3 is a characteristic diagram showing the relationship between the catalyst and the CO conversion rate. C.O.
A characteristic diagram showing the relationship between concentration and CO conversion rate, FIG. 4 is a schematic explanatory diagram of a carbon monoxide-containing air treatment apparatus in an embodiment of the present invention, FIGS. 5, 6, 7, and 8. Each figure is an explanatory diagram showing the shape of the catalyst. 1...Device body, 2...Motor, 3.
...Fan, 5...Secondary air intake port, 6
...Catalyst packed bed.

Claims (1)

[Claims] 1 A catalyst carrying a platinum metal element is placed in a kneaded material containing powdered activated carbon, an alkali, and a cement agent in contact with an air flow formed by forced flow or natural convection by a blower, and the alkali is potassium carbonate, A carbon monoxide-containing air treatment device that uses lime aluminate as the cement agent and platinum and palladium as the platinum metal elements.